Introduction to Forensic Chemistry

Detecting Metal Ions

Portugal (AEBarcelos)

By Carlota, Francisca, Eduarda André e Gonçalo

Metal Ions​

KA 229-School

Schools Challenge for Forensic Science

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Kolobrezeg (Poland) 2022​

By Carlota, Francisca, Eduarda André e Gonçalo

Forensic Chemistry​

• ​Is the application to analyze any non-biological materials found at a crime scene, and figure out how they connect to the person who committed the crime.

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• ​It must determine the chemical makeup of the material and discover where it came from.

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• A forensic chemist will perform various types of tests, depending on what the material is, to find where the material comes from.

• ​How do you know if a solution will form a precipitate?

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If an ion is insoluble based on the solubility rules, then it forms a solid with an ion from the other reactant.

• ​How can you tell if a precipitate has formed in solution quizlet?

​You can identify the precipitate directly by comparing it with solubility rules.

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If it is decreed insoluble by these rules, you know it is the precipitate of the reaction.

​What indicates a precipitation reaction?

​Key Points.

A precipitation reaction refers to the formation of an insoluble salt when two solutions containing soluble salts are combined.

The insoluble salt that falls out of solution is known as the precipitate, hence the reaction’s name.

​Laboratory tests are used to detect and identify gases and ions. Instrumental methods of analysis are faster, more accurate and more sensitive than these simple chemical tests.

​Testing for aqueous metal ions

​Dilute sodium hydroxide solution reacts with some metal ions in solution, forming metal hydroxides.

Some of these metal hydroxides are insoluble, so they appear as precipitates.

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For example,

​CuSO₄(aq) + 2NaOH(aq) → Na₂SO₄(aq) + Cu(OH)₂(s)

Multiple Choice

When solutions of two ionic compounds are combined and a solid forms, the process is called

• hydration

• solvation

• dissociation

• precipitation

Multiple Choice

Which of these results in the formation of a precipitate?

• AgNO₃(aq) + NaOH(aq)→

• Ba(NO₃)₂(aq) + CaCl₂(aq)→

• NaNO₃(aq) + KOH(aq)→

• More than one of these form precipitates

Multiple Choice

What is initially observed when sodium hydroxide is added in excess to a solution of Fe²⁺ ions?

• Green precipitate

• Brown precipitate

• Blue precipitate

• White precipitate

Multiple Choice

A green precipitate formed when sodium hydroxide is added to an unknown solution indicates the presence of.....

• Iron(III)

• Calcium

• Copper

• Iron(II)

Multiple Choice

Dilute sodium hydroxide can be added to an unknown solution to indicate the presence of....

• Iron(II)

• Iron(III)

• Copper

• All of them

Multiple Choice

A gas produced when nitric acid is added to an unknown solution indicates the presence of....

• Sulfate

• Carbonate

• Phosphate

• Nitrate

Multiple Choice

How can you tell if you have aluminium ions (Al³⁺) when you add sodium hydroxide and not zinc ions (Zn²⁺)?

• Get a white precipitate.
• Get a white precipitate that dissolves in excess sodium hydroxide
• Get a white precipitate that does not dissolve in an ammonia solution
• Get a white precipitate that does dissolve in an ammonia solution

Multiple Choice

Which of the following best describes the colour of $$Cu^{2+}$$  in aqueous solution?

• blue

• reddish brown

• silvery

• colourless

Multiple Choice

Which of the following best describes the colour of $$Co^{2+}$$  in aqueous solution?

• pink

• red

• green

• blue

Multiple Select

Which of the following ions is NOT yellow? (You may select more than 1 answer.)

• Ca²⁺

• CrO₄^2-

• Cr³⁺

• MnO₄^-

• Fe³⁺

Multiple Select

Select TWO from the following ions that could NOT be green.

• Cr³⁺

• Na⁺

• Ni²⁺

• Cu²⁺

• Cl^-

Multiple Select

Which of the following solution is coloured? (You may select more than 1 answer.)

• copper(II) nitrate

• sodium hydroxide

• potassium dichromate

• zinc chloride

• potassium permanganate

​Testing for blood Haemoglobin in blood contains iron(II) ions which are present even in dried blood left at a crime scene.

​Phenolphthalein reacts with hydrogen peroxide in the presence of hemoglobin to turn from colorless to pink.

Multiple Choice

Which test can determine if blood found at a crime scene is human?

• Luminol

• ELISA

• Kastle - Meyer

• Humo - Hemo

Multiple Choice

How are adults’ ABO blood groups determined?

• By checking the red blood cell antigens

• By checking the antibodies in the serum

• By blood group genotyping

• By checking the red blood cell antigens and antibodies in plasma

Multiple Choice

What test is this?

• Kastle-Meyers

• Hemastix

• Luminol

• Precipitin

Multiple Choice

What test is this?

• Kastle-Meyers

• Hemastix

• Luminol

• Precipitin

Multiple Choice

Is this human or animal blood?

• Human

• Animal

Multiple Choice

Is this human or animal blood?

• Human

• Animal